This invention relates to a vehicle headlight with a discharge bulb and more particularly, to a light-distribution subpattern forming headlight.
Recently, a discharge lamp has been employed as the light source of a vehicle headlight, because it is able to perform a high brightness irradiation.
In the case of a headlight having a discharge lamp, a light-distribution subpattern having an oblique cut line and a horizontal cut line is formed, the resultant pattern is high in distant recognition, and wide in irradiation angle.
The power of the discharge lamp is great. Hence, the light-distribution subpattern is formed by light reflected from a region of the reflecting surface which is only a substantially upper half of the reflecting surface with respect to the optical axis of the reflector.
As was described above, the light-distribution subpattern is formed only by the light reflected from the region of the reflector reflecting surface which is a substantially upper half thereof with respect to the optical axis of the reflector. However, the light advancing towards the remaining reflecting surface region is not used at all. This is not economical or efficient. In addition, in order to improved the traveling safety of a vehicle at night, it is desirable to utilize the output light of the discharge bulb as much as possible.